The present invention relates generally to multicolor display devices and, more particularly, to a method and apparatus for achieving multiple colors on an integrated chip.
Multicolor generation systems are used in a variety of applications including monitors (e.g., direct and projection televisions, computer monitors), macro-displays (e.g., billboards), and micro-displays (e.g., telephones and PDAs). Currently a number of different techniques are used to achieve multicolor displays. For example, depending upon application requirements such as contrast, brightness, color range, color accuracy, power consumption, size and cost, a display may utilize light generation systems based on everything from CRTs to LCDs.
Currently, the emphasis on full-featured microelectronic systems has resulted in manufacturers working to develop more efficient, multicolor displays that can replace the simple monotone displays common in such devices. Although LCD display based systems have proven adequate for some applications, device complexity and cost have prohibited their use for the majority of such systems. The present invention overcomes the obstacles associated with the prior approaches and provides a simple display device that can be tailored to meet varying color and display size requirements.
The present invention provides a method and apparatus for achieving multicolor displays using an integrated color chip. The integrated color chip contains one or more multicolor generation sites on a single substrate. Each multicolor generation site is comprised of two or more light emitting regions, preferably LEDs, in close enough proximity to one another to achieve color integration. The active light generation system for each light emitting region, e.g., an LED, is preferably identical in device structure although size and shape may vary. In order to achieve the desired colors, one or more light conversion layers are applied to individual light emitting regions. Thus, for example, a simple three color generation site may include three blue light emitting LEDs, one of which includes a blue-to-green light conversion layer and one of which includes a blue-to-red light conversion layer. Each light emitting region may also include index matching layers, preferably interposed between the outermost surface of the light emitter and the light conversion layer, and protective layers.
The number of required light emitting regions per multicolor generation site depends upon the application. For example, a two color system comprised of a blue color emitting region and a yellow color emitting region can be used to produce a range of colors, including white. Alternately, a complete color range can be achieved using a three color system comprised of three light emitting regions. Preferably the three light emitting regions in combination with the required light conversion layers emit three primary additives such as red light, green light, and blue light.
In at least one embodiment of the invention, opaque material is deposited between adjacent light emitting regions thereby minimizing cross-talk and achieving improved contrast. In at least one other embodiment of the invention, cross-talk due to substrate reflections is minimized by removing the light emitting regions from the substrate on which they were grown and affixing them to a secondary, support substrate. In at least one other embodiment of the invention, cross-talk due to substrate reflections is minimized by interposing an absorbing or partially reflective material between the substrate and the light emitting regions.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.